Dive Brief:

• Kauai Island Utility Cooperative (KIUC) and AES Corp. have executed and filed a power purchase agreement with Hawaii regulators to develop a solar-powered pumped hydro storage project the utility says will bring its total resource mix above 80% renewables.
• The West Kauai Energy Project could come online in 2024. A solar array will be capable of sending 35 MW directly to the island's grid and an associated battery will store up to 240 MWh for dispatch during evening peak. The hydro resources are expected to produce 24 MW on average daily, including 12 hours of storage to be used overnight
• KIUC says the project will meet about 25% of the island's electricity needs, and puts it on track to exceed the utility's target of reaching 70% renewable generation by 2030.

Dive Insight:

KIUC officials say there are a host of benefits attached to the solar+pumped hydro project, including lowering bills, raising renewable energy utilization and rehabilitating reservoirs that will also assist first responders in addressing wildfires.

"This project's integration of pump storage hydropower with large-scale solar power is unique in the energy industry," KIUC President and CEO David Bissell said in a statement. "Upon completion, the facility will operate at a cost that will benefit KIUC’s members for decades.”

The solar+battery system will provide power at a rate of $71.60/MWh, while the hydro project will require capacity payments of almost $9 million per year. The utility says the pumped hydropower will provide 12 hours of storage daily, compared with 4 to 5 hours of energy from existing solar+battery facilities.

"This long-duration storage capacity will allow the island to run on 100% renewable energy for prolonged periods without sunlight and will provide additional grid stability by balancing intermittent solar with firm hydropower," the utility said.

The project will "stabilize and lower electricity rates over time for our members, open up dormant agricultural lands for production, assure adequate streamflow and increase public access and recreational opportunities associated with the Pu‘u Lua Reservoir," Bissell said.

This is not the first project KIUC has undertaken with AES. Already complete are a pair of solar+storage projects, including a 20 MW facility in Lāwai and a 14 MW facility at the Pacific Missile Range Facility.

According to the utility, environmental studies for the West Kauai Energy Project are ongoing and a draft environmental assessment is expected to be filed with Hawaii Department of Land and Natural Resources in the first quarter of 2021. The power purchase agreement for the project was filed with the Hawaii Public Utilities Commission on Dec. 31, 2020.

KIUC says the project will offset the use of 8.5 million gallons of fossil fuels annually, potentially saving customers more than $170 million over the 25-year power purchase agreement, and will supply irrigation water delivery to support diversified agriculture on state lands. 

Last year, KIUC says it achieved $3.8 million in savings through its utility-scale solar and battery facilities, compare with the average cost of diesel.

CORRECTION: The previous headline of this article misnamed the utility involved. It is Kauai Island Utility Cooperative